Neutron Limit on the Strongly-Coupled Chameleon Field (original) (raw)
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Neutron interferometry constrains dark energy chameleon fields
Physics Letters B, 2015
We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant β is less than 1.9 ×10 7 for n = 1 at 95% confidence level, where n is an input parameter of the self-interaction of the chameleon field ϕ inversely proportional to ϕ n .
A sensitive search for dark energy through chameleon scalar fields using neutron interferometry
Journal of Physics: Conference Series, 2015
The physical origin of the dark energy, which is postulated to cause the accelerated expansion rate of the universe, is one of the major open questions of cosmology. A large subset of theories postulate the existence of a scalar field with a nonlinear coupling to matter chosen so that the effective range and/or strength of the field is greatly suppressed unless the source is placed in vacuum. We describe a measurement using neutron interferometry which can place a stringent upper bound on chameleon fields proposed as a solution to the problem of the origin of dark energy of the universe in the regime with a strongly-nolinear coupling term. In combination with other experiments searching for exotic short-range forces and laser-based measurements, slow neutron experiments are capable of eliminating this and many similar types of scalar-field-based dark energy models by laboratory experiments.
Proceedings of The European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2015), 2016
We report a measurement of the local acceleration with ultracold neutrons based on quantum states in the gravity potential of the Earth. The new method uses resonant transitions between the states |1 ↔ |3 and for the first time between |1 ↔ |4. The measurements demonstrate that Newton's Inverse Square Law of Gravity is understood at micron distances at an energy level of 10 −14 eV with ∆g g = 4 × 10 −3. The results provide constraints on any possible gravitylike interaction at a micrometer interaction range. In particular, a dark energy candidate, the chameleon field is restricted to β < 6.9 × 10 6 for n = 2 (95% C.L.).
Constraining the phase space for chameleon dark energy
2011
Abstract. A number of solutions to the dark energy problem have been proposed in literature, the simplest is the cosmological constant Λ. The cosmological constant lacks theoretical explanation for its extremely small value, thus dark energy is more generally modeled as quintessence scalar field rolling down a flat potential. For the quintessence scalar field to be evolving on cosmological scales to day its mass must be of order H0 , which is the present value of the Hubble constant. A scalar field φ whose mass varies with the background energy density was proposed by Khoury and Weltman. This scalar field can evolve cosmologically while having coupling to different matter fields of order unity. Such a scalar field also couples to photons in the presence of an external magnetic field via the φF 2 interaction, where F stands for the electromagnetic field strength tensor. The chameleon-photon coupling of this nature causes a conversion of photons to light Chameleon(φ) particles and vic...
Laboratory Constraints on Chameleon Dark Energy and Power-Law Fields
Physical Review Letters, 2010
We report results from the GammeV Chameleon Afterglow Search-a search for chameleon particles created via photon/chameleon oscillations within a magnetic field. This experiment is sensitive to a wide class of chameleon power-law models and dark energy models not previously explored. These results exclude five orders of magnitude in the coupling of chameleons to photons covering a range of four orders of magnitude in chameleon effective mass and, for individual chameleon models, exclude between 4 and 12 orders of magnitude in chameleon couplings to matter. PACS numbers: 95.36.+x, 95.35.+d, 14.80.Va,
2004
Chameleons are scalar fields whose mass depends on the environment, specifically on the ambient matter density. While nearly massless in the cosmos, where the matter density is tiny, their mass is of order of an inverse millimeter on Earth, where the density is high. In this note, we review how chameleons can satisfy current experimental constraints on deviations from General
Impact of dynamical dark energy on the neutron star equilibrium
Journal of Cosmology and Astroparticle Physics, 2021
We study the density distribution of the minimally-coupled scalar field dark energy inside a neutron star. The dark energy is considered in the hydrodynamical representation as a perfect fluid with three parameters (background density, equation of state, and effective sound speed). The neutron star matter is modeled with three unified equations of state, developed by the Brussels-Montreal group. With the calculated density distribution of the dark energy inside a neutron star (and its dependence on the dark energy parameters) we investigate how its presence impacts the macroscopic characteristics and the value of the mass limit for neutron stars. From this impact we derive the possible constrains on the effective speed of sound of dark energy with the help of maximal known masses of observed neutron stars. In this approach, we have found, that the squared effective speed of sound can not be smaller than ∼ 10 −2 in units of squared speed of light.
Tests of fundamental quantum mechanics and dark interactions with low-energy neutrons
Nature Reviews Physics, 2021
Among the known particles, the neutron takes a special position, as it provides experimental access to all four fundamental forces and a wide range of hypothetical interactions. Despite being unstable, free neutrons live long enough to be used as test particles in interferometric, spectroscopic, and scattering experiments probing low-energy scales. As was already recognized in the 1970s, fundamental concepts of quantum mechanics can be tested in neutron interferometry using silicon perfect-single-crystals. Besides allowing for tests of uncertainty relations, Bell inequalities and alike, neutrons offer the opportunity to observe the effects of gravity and hypothetical dark forces acting on extended matter wave functions. Such tests gain importance in the light of recent discoveries of inconsistencies in our understanding of cosmology as well as the incompatibility between quantum mechanics and general relativity. Experiments with low-energy neutrons are thus indispensable tools for probing fundamental physics and represent a complementary approach to colliders. In this review we discuss the history and experimental methods used at this low-energy frontier of physics and collect bounds and limits on quantum mechanical relations and dark energy interactions.